As the time lapses more and more particles will get accumulated. and what is the threshold value or quantity of diesel particles that has be considered.
On a DPF, carbon part of soot particles are reburnt.
It happens when exhaust gas are hot (for exemple when you climb a hill) to start combustion of carbon on the DPF. When carbon combustion is initiated, temperature is hot enough to sustain the combustion of all the carbon deposited.
If your way of driving does'nt permit to have hot gases the counter pressure rises and there is an information to the engine CPU to produce hot gases. It depends on the engine : late injection in the cycle or a fifth injector in the exhaust system.
For the mineral part of the soot, it accumulates and you have to clean the DPF after 120000 km for example.
Best regards
The DPF affects diesel engine performance in two ways.
[1] Engine efficiency decreases with increasing backpressure due to thermodynamic reasons. The pressure drop of the DPF increases as it captures particulate matter from the engine. Depending on the DPF wall material, cell density, diameter and brick length, a clean DPF typically has a baseline pressure drop of 0.5-0.8 kPa. A rule of thumb is that the engine power will decrease by 1% for every 3-4 kPa increase in engine backpressure. Thus, engine OEMs tend to limit engine backpressure to approximately 1.5 psi (10 kPa). Large backpressure not only reduces efficiency, but could also damage the engine.
[2] The DPF must be regenerated, continuously or intermittently. Continuous regeneration only occur when the exhaust gas temperature is higher than the soot-balancing temperature (SBT) for a significant fraction of time. This often requires high loading of PGM catalyst in the DPF washcoat. For non- or lightly catalyzed DPFs that typically operate below the SBT, active regeneration is required when the pressure drop exceeds a threshold, typically 5 to 7 kPa. To enable active regeneration event, the exhaust gas temperature must be raised to well above the SBT using extra heat generated either by the engine or by an auxiliary heat source. This, of course, consumes energy. Therefore, DPF regeneration, either active or passive, intermittent or continuous, comes with a fuel penalty.
This fuel penalty can be reduced through system optimization. For example, if the DPF can be regenerated by a stand-alone DPF regen system without engine intervention, the engine can be tuned back to the most efficient condition to deliver max power, so that the net fuel penalty can be minimized.
There is certainly an impact from exhaust backpressure due to DPF, DOC, NAC and SCR exhaust catalysts, but engines equipped with both DPF and NOx catalysts are still capable of over 28-bar peak BMEP and a best BSFC of less than 200 g/kW-hr. Systems on heavy-duty trucks with the SCR positioned downstream of the DPF can advance injection timing somewhat to lower soot loading on the DPF and improve BSFC, provide more NO2 for passive soot regeneration on the DPF, and rely primarily on the SCR system for deNOX. Such systems still have the capability of active soot regeneration but still rely primarily on passive regeneration.
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